I was going to say a "flipping idiot", but probably "flipping novice" is more appropriate.
– Hot LicksApr 28 '16 at 1:20

conceivably, you are the "presenter" (or indeed "presentor") and the other is the "presentee". this would only work in certain situations but it would be, uh, best in those situations.
– FattieApr 28 '16 at 12:53

One important word not mentioned here yet is witness. the person you demonstrate to would witness you "flipping a chair for him". witness also refers to someone who testifies in court for what they have witnessed.

I would use the term that fits the role or relationship. Are they there to learn or to evaluate? Or is the demonstration more of a dog and pony show intended for a general audience. Or are you accosting people on the street hawking your toy robots?

If you were just looking at the mechanics of demonstrations, I'd probably use recipients, audience, or participants in apposition to demonstrator.

There is the perfectly good word demonstratee ... it's not common but it is part of the English language. Given it's logical connection to demonstrator the meaning should be apparent to people who don't know it and it ties in to your view that you are demonstrating (as opposed to showing or teaching...).

@J Woodchuck I'm not the downvoter. But prior to the downvote, your answer was flagged, which prompted my comment to to you. The down vote may be for lack of support, or it may be that someone thought it wasn't a good answer. The downvoter should have explained the issue. Normally, either an edit fixes the issue, or the answer may be deleted. Sorry that you got hit by a random drive-by downvote on your first answer.
– Phil SweetApr 28 '16 at 4:08

@JWoodchuck Comments are transient, so it's always good to include your source in the answer itself. I've edited to include it. Thanks!
– Nathaniel is protestingApr 28 '16 at 4:14

The wealth of possible terms offered emphasizes the value of Phil Sweet's advice of April 25: each of the candidate terms has nuanced meaning that fits its context; select the one that best fits the role or relationship you are describing